Presently, there is general agreement that, while odontogenic keratocyst may be of varied origin, one clinical feature warrants its recognition and separation as a distinctive entity: the exceedingly high recurrence rate.We reported a case of odontogenic keratocyst extending from the second molar to the ramus of the right mandible with an impacted tooth in the mandibular condyle region.The patient, a 20-year-old woman, visited our hospital to examine the ramus of the right mandible.In radiological findings, from the 7 position to the ramus of mandible, a unilocular shadow with a scalloped periphery was observed.We operated on the mandibular resection from the 7 position to the ramus of mandible of the right side with mandibular condyle. Then we performed an immediate reconstructive operation of the mandible by autogeneus illiac bone grafting.The lingual cortical plate of the ramus of mandible was perforated.In histological findings, the lining epithelium of cyst wall was stratified squamous with parakeratosis. Epithelium was consisting of 6 or 8 ros of the cells, and showed dental laminalike epithelium.There is the cyst wall between the impacted tooth in the mandibular condyle region and the lumen of this cyst. The lumen of this cyst was filled with a thicker creamy material.Two years have passed since the operation and the prognosis is favorable without recurrence.